The United States is divided into a plurality of contiguous, non-overlapping exchanges, referred to as Local Access Transport Areas (LATAs), each of which is served by a local telephone company. Telephone calls originating and terminating within the same exchange, referred to as intra-exchange calls, are handled end-to-end by a local, intra-exchange, telephone company. Calls originating within one exchange or in a foreign country and terminating in a different exchange or in a foreign country, referred to as inter-exchange calls, are handled at each end by the intra-exchange company that services the originating and the terminating exchanges. These inter-exchange calls are carried between the intra-exchange companies by one or more inter-exchange carriers.
A caller who wishes to select an inter-exchange carrier must dial special access codes that are assigned to each inter-exchange carrier and once connected, must also dial a personal identification code and the number of the called party to have the call completed. With the proliferation of inter-exchange carriers, carrier selection is often difficult for a telephone communication system user. The user may be unaware of which inter-exchange carrier is the most economical for a particular time of day, which inter-exchange carrier serves the user's telephone communication system or what access codes are appropriate for the particular inter-exchange carriers available to the user's telephone communication system.
During the last few years, the competition between telephone companies (also known as "operating companies" or "service providers") for the telephone subscribers business has increased markedly. This competition is most evident in the multiplicity of tariffs from each carrier, which vary not only between destinations but also vary according to the time of day and the length of call. Also competition exists between intra-exchange service providers.
Though this competition gives the customer an opportunity for significant money saving, the customer rarely benefits fully because of the complexity and the variety of tariffs. For example, tariffs may vary due to the time of day, on weekends, holidays, according to the call destination and method of payment. The situation may be further complicated by special limited discounts offered by the telephone companies, the entry of new telephone companies to new markets and the grade of service requested (such as voice quality and connection delays).
The entry of new money saving services, such as Fax Store and Forward and call-back services, the availability of alternate services offered by private networks using their own PBX and the usage of corporate networks are additional factors affecting the cost of the call. Consequently, the customer has to contend with a huge amount of information in order to make a simple telephone call.
U.S. Pat. No. 4,791,665 to Bogart et al. describes a telephone communication system (PBXs) with the capability of automatically selecting one of a plurality of inter-exchange carriers. The system includes a database containing access code data associated with the inter-exchange carriers, user authorization codes and information about the various inter-exchange carrier billing rates based on time of day and destination. The PBX scans the database and reroutes the originating call to one of the other inter-exchange carriers having a cheaper tariff for the particular destination at the specific time of day. The PBX sends out the inter-exchange carrier access code, the user's personal identification code and the called party number dialed by the user to complete the call.
U.S. Pat. No. 5,425,084 to Brinskele describes a computer controlled telephone communication system which includes a plurality of digital switches each located in different charge zones. Each digital switch is coupled to a file server which determines which of the digital switches to use in order to ensure the lowest possible cost for the call.
U.S. Pat. No. 5,420,914 to Blumhardt describes a real time selection of one of a plurality of inter-exchange carriers which automatically selects the carrier having the least expensive toll at the time the call is made and reroutes the call accordingly. Blumhardt is used in conjunction with an advanced intelligent network (AIN) in a public switched telephone network (PSTN).
In prior art least cost routing systems, updating the tariff database is very complicated since the interface to do so is cumbersome. Therefore, the operators of the least cost routing system rarely update their tariff databases. As a result, the routing decision taken may not necessarily be the optimum route for the call, at that time.